1. Technical Field
The present invention relates to a belt transport device including a drive roller which is driven by a power source, a driven roller which is held in a rotatable manner, an endless belt which is wound on the drive roller and the driven roller, a band-like detecting section which is arranged on the endless belt in a circumferential direction of the endless belt, and a sensor which detects the band-like detecting section, and a belt transport control method.
2. Related Art
In the past, as disclosed in JP-A-8-211693, JP-A-2006-248082 and Japanese Patent No. 3082452, belt transport devices had a drive roller, a driven roller and an endless belt. In addition, a detecting section was provided on the endless belt and a detector was provided at a position opposed to the detecting section. Accordingly, while the endless belt rotated in a circumferential direction of the belt, the detector was able to detect information such as positional information from the detecting section.
However, there is a possibility that the detector may trace the same point in the detecting section when the endless belt circulates.
For example, when the endless belt does not obliquely travel and circulates, the detector traces the same point in the detecting section in a width direction.
When a configuration for controlling the oblique traveling of the endless belt is employed and the endless belt circulates, there is a possibility that the detector may trace the same point in the detecting section in the width direction in accordance with an oblique traveling cycle of the endless belt.
FIGS. 7A to 7C are schematic diagrams illustrating a relationship between an oblique traveling cycle of an endless belt according to a related art and a revolution cycle of the endless belt.
As illustrated in FIGS. 7A to 7C, a detecting section 30 having a width W is provided over the whole area in a circumferential direction of the endless belt and over a part of the area in a width direction of the endless belt. When L is a length of one revolution of the endless belt, a relative positional relationship between a sensor 31 and the detecting section 30 provided on the endless belt is displaced by the oblique traveling of the endless belt.
Herein, as illustrated in FIG. 7A, when an oblique traveling cycle Tx of the endless belt is equal to a revolution cycle Ty of the endless belt, the sensor 31 always traces the same point in the detecting section 30.
Further, as illustrated in FIG. 7B, when a relationship between the oblique traveling cycle Tx of the endless belt and the revolution cycle Ty of the endless belt satisfies the expression Tx=½×Ty, the sensor 31 always traces the same point in the detecting section 30.
Furthermore, as illustrated in FIG. 7C, when a relationship between the oblique traveling cycle Tx of the endless belt and the revolution cycle Ty of the endless belt satisfies the expression Tx=2×Ty, the sensor 31 traces at least the same point in a central part of the width W. In addition, the sensor 31 traces the same point in the detecting section 30 for every two revolution of the endless belt.
Accordingly, when the sensor 31 is a contact sensor, only the same point in the detecting section 30 is worn and thus durability is deteriorated. Moreover, there is a possibility that an error may occur in detection as the wearing progresses. Even when the sensor 31 is a non-contact sensor, there is a significantly increasing possibility that an error may occur in detection when foreign materials adhere to the same point in the detecting section 30.